In conventional air compressors such as those used on internal combustion engines, exhaust gas energy is used to compress engine intake air. In certain other applications, so called superchargers are driven directly with mechanical engine power or an electric motor to compress air that is then provided pressurized to engine cylinders. In other applications, so called turbochargers are used, which include a turbine that receives pressurized exhaust gas from the engine. The exhaust gas passes through a scrolled passage of the turbine and impinges onto a turbine wheel causing it to turn. The turbine wheel is connected to a shaft, which is connected to a compressor wheel disposed in a compressor housing. The powered rotation of the turbine wheel and shaft operate to turn the compressor wheel, which draws air into a compressor housing having a scrolled shape and compresses it.
Various types, sizes and numbers of turbochargers and/or superchargers have been used on engines in the past. One design consideration when selecting an appropriate compressor for an engine application is the air flow rate and desired pressure ratio of engine intake air. Further, because air compression increases the temperature of the compressed air, engines typically use heat exchangers, such as air-to-air heat exchangers, to cool the compressed air before it is delivered to the engine.
In certain turbocharger applications, the compressor and turbine wheels are interconnected by a shaft such that they rotate in unison. A center housing disposed between the turbine and compressor machines rotatably supports the shaft using bearings. These bearings, which may be of any known type, may use engine oil for operation, lubrication, cooling and the like. Oil is provided to the center housing, typically from the engine, and flows through the center housing while the engine operates. The oil flowing through the center housing washes over bearings supporting the shaft. In certain engine operating conditions, oil present within the center housing may leak into an operating chamber of the turbine and/or compressor housings of the turbocharger. Such oil leakage may contaminate exhaust after treatment components and/or various engine components.